Thermal control of audio playback devices

ABSTRACT

To avoid damage from overheating, playback device operation can be modulated based on input from temperature sensors. An example method includes obtaining, via one or more temperature sensors carried by the playback device, temperature data. Based on the temperature data, a first temperature parameter is detected. In response to detecting the first temperature parameter, a gain of audio playback is decreased by a first amount. After decreasing the gain of audio playback by the first amount, a second temperature parameter is detected. In response to detecting the second temperature parameter, the gain of audio playback is decreased by a second amount different than the first amount.

CROSS-REFERENCE TO RELATED APPLICATION

The present application is a continuation of U.S. patent applicationSer. No. 17/301,012, filed Mar. 22, 2021, which claims the benefit ofpriority to U.S. Patent Application No. 62/994,720, filed Mar. 25, 2020,which are incorporated herein by reference in their entireties.

FIELD OF THE DISCLOSURE

The present disclosure is related to consumer goods and, moreparticularly, to methods, systems, products, features, services, andother elements directed to media playback or some aspect thereof.

BACKGROUND

Options for accessing and listening to digital audio in an out-loudsetting were limited until in 2002, when SONOS, Inc. began developmentof a new type of playback system. Sonos then filed one of its firstpatent applications in 2003, entitled “Method for Synchronizing AudioPlayback between Multiple Networked Devices,” and began offering itsfirst media playback systems for sale in 2005. The Sonos Wireless HomeSound System enables people to experience music from many sources viaone or more networked playback devices. Through a software controlapplication installed on a controller (e.g., smartphone, tablet,computer, voice input device), one can play what she wants in any roomhaving a networked playback device. Media content (e.g., songs,podcasts, video sound) can be streamed to playback devices such thateach room with a playback device can play back corresponding differentmedia content. In addition, rooms can be grouped together forsynchronous playback of the same media content, and/or the same mediacontent can be heard in all rooms synchronously.

BRIEF DESCRIPTION OF THE DRAWINGS

Features, examples, and advantages of the presently disclosed technologymay be better understood with regard to the following description,appended claims, and accompanying drawings, as listed below. A personskilled in the relevant art will understand that the features shown inthe drawings are for purposes of illustrations, and variations,including different and/or additional features and arrangements thereof,are possible.

FIG. 1A is a partial cutaway view of an environment having a mediaplayback system configured in accordance with examples of the disclosedtechnology.

FIG. 1B is a schematic diagram of the media playback system of FIG. 1Aand one or more networks.

FIG. 1C is a block diagram of a playback device.

FIG. 1D is a block diagram of a playback device.

FIG. 1E is a block diagram of a network microphone device.

FIG. 1F is a block diagram of a network microphone device.

FIG. 1G is a block diagram of a playback device.

FIG. 1H is a partially schematic diagram of a control device. FIG. 2A isa front isometric view of a playback device configured in accordancewith examples of the disclosed technology.

FIG. 2B is a front isometric view of the playback device of FIG. 2Awithout a grille.

FIG. 2C is an exploded view of the playback device of FIG. 2A.

FIG. 3 is a schematic block diagram of a thermal control system for aplayback device in accordance with examples of the present technology.

FIG. 4 is a flow diagram of a method for thermal control of a playbackdevice.

FIG. 5 is a graph showing temperature over time during thermal controlprocesses in accordance with examples of the present technology.

FIG. 6 is a graph showing gain reduction over time during thermalcontrol processes in accordance with examples of the present technology.

The drawings are for the purpose of illustrating examples of the presenttechnology, but those of ordinary skill in the art will understand thatthe technology disclosed herein is not limited to the arrangementsand/or instrumentality shown in the drawings.

DETAILED DESCRIPTION I. Overview

Audio playback devices can produce significant amount of heat thatvaries greatly depending on the operations conditions. If a playbackdevice is exposed to excessive temperature conditions, performance maydegrade and/or components of the playback device may be damaged. Forexample, a playback device may include power supply components thatautomatically shut off above a certain temperature threshold.Additionally, high temperature conditions can cause failure of computermemory, degradation of the enamel of transformers and voice coils,de-magnetization of transducer magnets, or melting of glue used to holdcomponents of the playback device together.

Conventionally, thermal damage has been avoided by over-engineeringaudio playback devices so that even under maximum operating conditions(e.g., high ambient temperature, full-volume audio playback, high datatransmission via Wi-Fi, etc.), the components are able to withstand theassociated temperature levels. However, such over-engineering isexpensive and relatively inefficient, since mass-produced devices mustbe designed to accommodate operating conditions that prevail in only atiny fraction of real-world situations.

Another approach to avoiding thermal damage is to shut down some or allfunctions of a playback device altogether once a temperature thresholdhas been exceeded. For example, once an audio playback device hasexceeded 100 degrees C., the device may be completely shut down.Alternatively, certain functions (e.g., Wi-Fi transmission, or audioplayback) may be completely shut down while other functions remainoperational. In either case, the user experience is negatively impacted,as the playback device abruptly ceases functioning as a result of thehigh temperature.

To avoid these and other deleterious consequences of excessivetemperature, embodiments of the present technology include a thermalcontroller configured to monitor the temperature of a playback deviceand make real-time adjustments to audio playback or other deviceoperation to avoid thermal damage. As opposed completely shutting downthe device or abruptly terminating audio playback, the intervention canmore selectively modulate audio playback or other device operation in amanner that both preserves the user experience while also reducing thethermal load until the temperature has fallen back to an acceptablelevel.

Adjusting audio playback can include, for example reducing a gain ofaudio playback (e.g., full-spectrum reduction in amplitude of audioplayback for all transducers of a playback device). In some examples,audio playback can be modified in other ways to reduce the temperature.For example, gain reduction may be varied across frequency ranges, suchas larger gain reductions in lower frequencies and smaller gainreductions in higher frequencies. In some cases, gain reduction may beapplied to some but not all of the transducers, or the amount of gainreduction may vary across the transducers. In some embodiments, otherdevice operations can be modulated in response to excessive heat—forexample Bluetooth connectivity may be temporarily disabled, Wi-Fi datatransmission can be throttled, processor operation may be constrainedwithout fully shutting down, etc.

In some examples, a playback device includes one or more temperaturesensors disposed on, within, or about the device and configured toprovide real-time temperature data. In operation, the temperaturesensor(s) can obtain temperature data used to determine whether apre-determined threshold temperature has been exceeded. For example,above a first or lower temperature threshold, the thermal controller mayinitiate modulation of device operation (e.g., once the temperatureexceeds 60 degrees C., a gain reduction or other intervention begins tobe applied). If, following the modulation, the temperature falls belowthe lower temperature threshold, then the modulation (e.g., gainreduction) can be ceased, and the playback device can resume normaloperation. If, instead, the temperature stays above the lowertemperature threshold, then device operation can continue to bemodulated via the thermal controller, with the degree of modulation(e.g., amount of gain reduction) depending on the particular temperaturedata obtained via the sensors. For example, as the temperature continuesto increase beyond the lower temperature threshold, the amount of gainreduction can be increasingly large. If the temperature continues toincrease and further exceeds a second or upper temperature threshold(e.g., a maximum safe operating temperature of the playback device),audio playback or other device operation can be suspended and/or thedevice may be shut down completely. This scenario indicates a failure ofthe modulation via the thermal controller to reduce the temperature tosafe operating levels, and so performance is sacrificed in order toprotect the playback device.

In some cases, once the lower threshold temperature has been exceeded,the degree of modulation (e.g., the amount of gain reduction applied toaudio playback) can vary depending on the particular temperatureincrease detected by the temperature sensor(s). In some examples, dataobtained via the temperature sensors can be evaluated to determine oneor more of: (1) whether the temperature has exceeded the lowertemperature threshold; (2) whether the temperature has exceeded theupper temperature threshold; and (3) a temperature parameter thatcharacterizes the change in temperature. The modulation applied (e.g.,amount of gain reduction) can be varied based on the temperatureparameter, with increasingly robust interventions (e.g., higher gainreductions) applied as the temperature parameter rises (e.g., indicatinga higher rate of temperature increase).

The temperature parameter can include, for example, an absolutetemperature amount over or above a threshold (e.g., degrees C. beyondthe lower threshold), a rate of temperature increase or decrease overtime (e.g., degrees C. of increase per second), or other such parameter.In some examples, the temperature parameter includes a time elapsedsince the last temperature increase of a pre-determined amount has beendetected (e.g., time elapsed since the temperature last increased by atleast 1 degree C. over the sampling period of the sensor (e.g., sampledevery 10 seconds). In some embodiments, a lookup table or function candefine an amount of gain reduction to be applied to audio playback thatis dependent on the time elapsed since the last detected rise intemperature of a pre-determined amount. As the rate of temperatureincrease goes up (as indicated by a decreasing amount of time since thelast measured increase of at least 1 degree C.), the amount of gainreduction can be increased.

The heat at any given position of the playback device can be a functionof environmental conditions (e.g., ambient temperature of thesurrounding air, humidity, etc.), as well as the heat generated fromdifferent components of the device (e.g., heat generated by electroniccomponents of a playback device (e.g., Wi-Fi chip, CPU, amplifiers,etc.). As a result, the temperature may vary across the playback device.It can therefore be useful to provide a plurality of discretetemperature sensors distributed about the device, each configured toobtain temperature data for its respective location. If the temperatureat any given location exceeds a threshold (as determined by data fromone or more of the temperature sensors), audio playback can be adjustedaccordingly.

In some embodiments, in addition to one or more physical temperaturesensors, one or more virtual sensors can be disposed about the device.Such virtual sensors can represent a predictive model that estimates ormodels the temperature at a particular location based on, among otherthings, temperature data from other physical temperature sensorsdisposed about the device. Such models may also take into account thematerial properties or elements at or adjacent to the location of thevirtual sensor. For example, a virtual sensor may be positioned in anintermediate area between three physical temperature sensors. Thevirtual sensor can be output a predicted temperature at this locationthat is based on temperature readings from the three physicaltemperature sensors, as well as material properties or other aspects ofthe playback device at or adjacent to the location of the virtualsensor. Throughout this description, a virtual sensor can be used inconjunction with or instead of any one or more of the physicaltemperature sensors described herein.

In some embodiments, the particular thresholds (e.g., a lower thresholdabove which playback device operation is modulated, and/or an upperthreshold above which the playback device is shut down completely)and/or the particular modulation (e.g., the amount of gain reductioncorresponding to a particular temperature parameter) can vary from onetemperature sensor to the next. For example, one temperature sensor maybe located next to a CPU which cannot safely exceed 100 degrees C.,while another temperature sensor may be located next to a transducerthat can operate safely until 120 degrees C. In such cases, thetemperature thresholds at which the thermal controller initiatesmodulation of playback device operation can be different between the twosensors.

A thermal controller in accordance with examples of the presenttechnology can advantageously modulate audio playback or other deviceoperation based on a real-time or substantially real-time feedback looputilizing data collected from one or more temperature sensors. Bytailoring the particular modulation to both the temperature level andthe magnitude of the temperature increase, a thermal controller canmodulate playback device performance to maintain safe operatingconditions while also preserving the user's experience by avoidingshutting down operation of the playback device until absolutelynecessary.

While some examples described herein may refer to functions performed bygiven actors such as “users,” “listeners,” and/or other entities, itshould be understood that this is for purposes of explanation only. Theclaims should not be interpreted to require action by any such exampleactor unless explicitly required by the language of the claimsthemselves.

In the Figures, identical reference numbers identify generally similar,and/or identical, elements. To facilitate the discussion of anyparticular element, the most significant digit or digits of a referencenumber refers to the Figure in which that element is first introduced.For example, element 110 a is first introduced and discussed withreference to FIG. 1A. Many of the details, dimensions, angles and otherfeatures shown in the Figures are merely illustrative of particularexamples of the disclosed technology. Accordingly, other examples canhave other details, dimensions, angles and features without departingfrom the spirit or scope of the disclosure. In addition, those ofordinary skill in the art will appreciate that further examples of thevarious disclosed technologies can be practiced without several of thedetails described below.

II. Suitable Operating Environment

FIG. 1A is a partial cutaway view of a media playback system 100distributed in an environment 101 (e.g., a house). The media playbacksystem 100 comprises one or more playback devices 110 (identifiedindividually as playback devices 110 a-n), one or more networkmicrophone devices (“NMDs”), 120 (identified individually as NMDs 120a-c), and one or more control devices 130 (identified individually ascontrol devices 130 a and 130 b).

As used herein the term “playback device” can generally refer to anetwork device configured to receive, process, and output data of amedia playback system. For example, a playback device can be a networkdevice that receives and processes audio content. In some examples, aplayback device includes one or more transducers or speakers powered byone or more amplifiers. In other examples, however, a playback deviceincludes one of (or neither of) the speaker and the amplifier. Forinstance, a playback device can comprise one or more amplifiersconfigured to drive one or more speakers external to the playback devicevia a corresponding wire or cable.

Moreover, as used herein the term NMD (i.e., a “network microphonedevice”) can generally refer to a network device that is configured foraudio detection. In some examples, an NMD is a stand-alone deviceconfigured primarily for audio detection. In other examples, an NMD isincorporated into a playback device (or vice versa).

The term “control device” can generally refer to a network deviceconfigured to perform functions relevant to facilitating user access,control, and/or configuration of the media playback system 100.

Each of the playback devices 110 is configured to receive audio signalsor data from one or more media sources (e.g., one or more remoteservers, one or more local devices) and play back the received audiosignals or data as sound. The one or more NMDs 120 are configured toreceive spoken word commands, and the one or more control devices 130are configured to receive user input. In response to the received spokenword commands and/or user input, the media playback system 100 can playback audio via one or more of the playback devices 110. In certainexamples, the playback devices 110 are configured to commence playbackof media content in response to a trigger. For instance, one or more ofthe playback devices 110 can be configured to play back a morningplaylist upon detection of an associated trigger condition (e.g.,presence of a user in a kitchen, detection of a coffee machineoperation). In some examples, for instance, the media playback system100 is configured to play back audio from a first playback device (e.g.,the playback device 110 a) in synchrony with a second playback device(e.g., the playback device 110 b). Interactions between the playbackdevices 110, NMDs 120, and/or control devices 130 of the media playbacksystem 100 configured in accordance with the various examples of thedisclosure are described in greater detail below.

In the illustrated example of FIG. 1A, the environment 101 comprises ahousehold having several rooms, spaces, and/or playback zones, including(clockwise from upper left) a master bathroom 101 a, a master bedroom101 b, a second bedroom 101 c, a family room or den 101 d, an office 101e, a living room 101 f, a dining room 101 g, a kitchen 101 h, and anoutdoor patio 101 i. While certain examples and examples are describedbelow in the context of a home environment, the technologies describedherein may be implemented in other types of environments. In someexamples, for instance, the media playback system 100 can be implementedin one or more commercial settings (e.g., a restaurant, mall, airport,hotel, a retail or other store), one or more vehicles (e.g., a sportsutility vehicle, bus, car, a ship, a boat, an airplane), multipleenvironments (e.g., a combination of home and vehicle environments),and/or another suitable environment where multi-zone audio may bedesirable.

The media playback system 100 can comprise one or more playback zones,some of which may correspond to the rooms in the environment 101. Themedia playback system 100 can be established with one or more playbackzones, after which additional zones may be added, or removed to form,for example, the configuration shown in FIG. 1A. Each zone may be givena name according to a different room or space such as the office 101 e,master bathroom 101 a, master bedroom 101 b, the second bedroom 101 c,kitchen 101 h, dining room 101 g, living room 101 f, and/or the balcony101 i. In some examples, a single playback zone may include multiplerooms or spaces. In certain examples, a single room or space may includemultiple playback zones.

In the illustrated example of FIG. 1A, the master bathroom 101 a, thesecond bedroom 101 c, the office 101 e, the living room 101 f, thedining room 101 g, the kitchen 101 h, and the outdoor patio 101 i eachinclude one playback device 110, and the master bedroom 101 b and theden 101 d include a plurality of playback devices 110. In the masterbedroom 101 b, the playback devices 110 l and 110 m may be configured,for example, to play back audio content in synchrony as individual onesof playback devices 110, as a bonded playback zone, as a consolidatedplayback device, and/or any combination thereof. Similarly, in the den101 d, the playback devices 110 h-j can be configured, for instance, toplay back audio content in synchrony as individual ones of playbackdevices 110, as one or more bonded playback devices, and/or as one ormore consolidated playback devices. Additional details regarding bondedand consolidated playback devices are described below with respect toFIGS. 1B and 1E.

In some examples, one or more of the playback zones in the environment101 may each be playing different audio content. For instance, a usermay be grilling on the patio 101 i and listening to hip hop music beingplayed by the playback device 110 c while another user is preparing foodin the kitchen 101 h and listening to classical music played by theplayback device 110 b. In another example, a playback zone may play thesame audio content in synchrony with another playback zone. Forinstance, the user may be in the office 101 e listening to the playbackdevice 110 f playing back the same hip-hop music being played back byplayback device 110 c on the patio 101 i. In some examples, the playbackdevices 110 c and 110 f play back the hip hop music in synchrony suchthat the user perceives that the audio content is being playedseamlessly (or at least substantially seamlessly) while moving betweendifferent playback zones. Additional details regarding audio playbacksynchronization among playback devices and/or zones can be found, forexample, in U.S. Pat. No. 8,234,395 entitled, “System and method forsynchronizing operations among a plurality of independently clockeddigital data processing devices,” which is incorporated herein byreference in its entirety.

a. Suitable Media Playback System

FIG. 1B is a schematic diagram of the media playback system 100 and acloud network 102. For ease of illustration, certain devices of themedia playback system 100 and the cloud network 102 are omitted fromFIG. 1B. One or more communication links 103 (referred to hereinafter as“the links 103”) communicatively couple the media playback system 100and the cloud network 102.

The links 103 can comprise, for example, one or more wired networks, oneor more wireless networks, one or more wide area networks (WAN), one ormore local area networks (LAN), one or more personal area networks(PAN), one or more telecommunication networks (e.g., one or more GlobalSystem for Mobiles (GSM) networks, Code Division Multiple Access (CDMA)networks, Long-Term Evolution (LTE) networks, 5G communication networknetworks, and/or other suitable data transmission protocol networks),etc. The cloud network 102 is configured to deliver media content (e.g.,audio content, video content, photographs, social media content) to themedia playback system 100 in response to a request transmitted from themedia playback system 100 via the links 103. In some examples, the cloudnetwork 102 is further configured to receive data (e.g. voice inputdata) from the media playback system 100 and correspondingly transmitcommands and/or media content to the media playback system 100.

The cloud network 102 comprises computing devices 106 (identifiedseparately as a first computing device 106 a, a second computing device106 b, and a third computing device 106 c). The computing devices 106can comprise individual computers or servers, such as, for example, amedia streaming service server storing audio and/or other media content,a voice service server, a social media server, a media playback systemcontrol server, etc. In some examples, one or more of the computingdevices 106 comprise modules of a single computer or server. In certainexamples, one or more of the computing devices 106 comprise one or moremodules, computers, and/or servers. Moreover, while the cloud network102 is described above in the context of a single cloud network, in someexamples the cloud network 102 comprises a plurality of cloud networkscomprising communicatively coupled computing devices. Furthermore, whilethe cloud network 102 is shown in FIG. 1B as having three of thecomputing devices 106, in some examples, the cloud network 102 comprisesfewer (or more than) three computing devices 106.

The media playback system 100 is configured to receive media contentfrom the networks 102 via the links 103. The received media content cancomprise, for example, a Uniform Resource Identifier (URI) and/or aUniform Resource Locator (URL). For instance, in some examples, themedia playback system 100 can stream, download, or otherwise obtain datafrom a URI or a URL corresponding to the received media content. Anetwork 104 communicatively couples the links 103 and at least a portionof the devices (e.g., one or more of the playback devices 110, NMDs 120,and/or control devices 130) of the media playback system 100. Thenetwork 104 can include, for example, a wireless network (e.g., a Wi-Finetwork, a Bluetooth, a Z-Wave network, a ZigBee, and/or other suitablewireless communication protocol network) and/or a wired network (e.g., anetwork comprising Ethernet, Universal Serial Bus (USB), and/or anothersuitable wired communication). As those of ordinary skill in the artwill appreciate, as used herein, “Wi-Fi” can refer to several differentcommunication protocols including, for example, Institute of Electricaland Electronics Engineers (IEEE) 802.11a, 802.11b, 802.11g, 802.11n,802.11ac, 802.11ac, 802.11ad, 802.11af, 802.11ah, 802.11ai, 802.11aj,802.11aq, 802.11ax, 802.11ay, 802.15, etc. transmitted at 2.4 Gigahertz(GHz), 5 GHz, and/or another suitable frequency.

In some examples, the network 104 comprises a dedicated communicationnetwork that the media playback system 100 uses to transmit messagesbetween individual devices and/or to transmit media content to and frommedia content sources (e.g., one or more of the computing devices 106).In certain examples, the network 104 is configured to be accessible onlyto devices in the media playback system 100, thereby reducinginterference and competition with other household devices. In otherexamples, however, the network 104 comprises an existing householdcommunication network (e.g., a household Wi-Fi network). In someexamples, the links 103 and the network 104 comprise one or more of thesame networks. In some examples, for instance, the links 103 and thenetwork 104 comprise a telecommunication network (e.g., an LTE network,a 5G network). Moreover, in some examples, the media playback system 100is implemented without the network 104, and devices comprising the mediaplayback system 100 can communicate with each other, for example, viaone or more direct connections, PANs, telecommunication networks, and/orother suitable communication links.

In some examples, audio content sources may be regularly added orremoved from the media playback system 100. In some examples, forinstance, the media playback system 100 performs an indexing of mediaitems when one or more media content sources are updated, added to,and/or removed from the media playback system 100. The media playbacksystem 100 can scan identifiable media items in some or all foldersand/or directories accessible to the playback devices 110, and generateor update a media content database comprising metadata (e.g., title,artist, album, track length) and other associated information (e.g.,URIs, URLs) for each identifiable media item found. In some examples,for instance, the media content database is stored on one or more of theplayback devices 110, network microphone devices 120, and/or controldevices 130.

In the illustrated example of FIG. 1B, the playback devices 110 l and110 m comprise a group 107 a. The playback devices 110 l and 110 m canbe positioned in different rooms in a household and be grouped togetherin the group 107 a on a temporary or permanent basis based on user inputreceived at the control device 130 a and/or another control device 130in the media playback system 100. When arranged in the group 107 a, theplayback devices 110 l and 110 m can be configured to play back the sameor similar audio content in synchrony from one or more audio contentsources. In certain examples, for instance, the group 107 a comprises abonded zone in which the playback devices 110 l and 110 m comprise leftaudio and right audio channels, respectively, of multi-channel audiocontent, thereby producing or enhancing a stereo effect of the audiocontent. In some examples, the group 107 a includes additional playbackdevices 110. In other examples, however, the media playback system 100omits the group 107 a and/or other grouped arrangements of the playbackdevices 110.

The media playback system 100 includes the NMDs 120 a and 120 d, eachcomprising one or more microphones configured to receive voiceutterances from a user. In the illustrated example of FIG. 1B, the NMD120 a is a standalone device and the NMD 120 d is integrated into theplayback device 110 n. The NMD 120 a, for example, is configured toreceive voice input 121 from a user 123. In some examples, the NMD 120 atransmits data associated with the received voice input 121 to a voiceassistant service (VAS) configured to (i) process the received voiceinput data and (ii) transmit a corresponding command to the mediaplayback system 100. In some examples, for instance, the computingdevice 106 c comprises one or more modules and/or servers of a VAS(e.g., a VAS operated by one or more of SONOS®, AMAZON®, GOOGLE® APPLE®,MICROSOFT®). The computing device 106 c can receive the voice input datafrom the NMD 120 a via the network 104 and the links 103. In response toreceiving the voice input data, the computing device 106 c processes thevoice input data (i.e., “Play Hey Jude by The Beatles”), and determinesthat the processed voice input includes a command to play a song (e.g.,“Hey Jude”). The computing device 106 c accordingly transmits commandsto the media playback system 100 to play back “Hey Jude” by the Beatlesfrom a suitable media service (e.g., via one or more of the computingdevices 106) on one or more of the playback devices 110.

b. Suitable Playback Devices

FIG. 1C is a block diagram of the playback device 110 a comprising aninput/output 111. The input/output 111 can include an analog I/O 111 a(e.g., one or more wires, cables, and/or other suitable communicationlinks configured to carry analog signals) and/or a digital I/O 111 b(e.g., one or more wires, cables, or other suitable communication linksconfigured to carry digital signals). In some examples, the analog I/O111 a is an audio line-in input connection comprising, for example, anauto-detecting 3.5 mm audio line-in connection. In some examples, thedigital I/O 111 b comprises a Sony/Philips Digital Interface Format(S/PDIF) communication interface and/or cable and/or a Toshiba Link(TOSLINK) cable. In some examples, the digital I/O 111 b comprises aHigh-Definition Multimedia Interface (HDMI) interface and/or cable. Insome examples, the digital I/O 111 b includes one or more wirelesscommunication links comprising, for example, a radio frequency (RF),infrared, WiFi, Bluetooth, or another suitable communication protocol.In certain examples, the analog I/O 111 a and the digital 111 b compriseinterfaces (e.g., ports, plugs, jacks) configured to receive connectorsof cables transmitting analog and digital signals, respectively, withoutnecessarily including cables.

The playback device 110 a, for example, can receive media content (e.g.,audio content comprising music and/or other sounds) from a local audiosource 105 via the input/output 111 (e.g., a cable, a wire, a PAN, aBluetooth connection, an ad hoc wired or wireless communication network,and/or another suitable communication link). The local audio source 105can comprise, for example, a mobile device (e.g., a smartphone, atablet, a laptop computer) or another suitable audio component (e.g., atelevision, a desktop computer, an amplifier, a phonograph, a Blu-rayplayer, a memory storing digital media files). In some examples, thelocal audio source 105 includes local music libraries on a smartphone, acomputer, a networked-attached storage (NAS), and/or another suitabledevice configured to store media files. In certain examples, one or moreof the playback devices 110, NMDs 120, and/or control devices 130comprise the local audio source 105. In other examples, however, themedia playback system omits the local audio source 105 altogether. Insome examples, the playback device 110 a does not include aninput/output 111 and receives all audio content via the network 104.

The playback device 110 a further comprises electronics 112, a userinterface 113 (e.g., one or more buttons, knobs, dials, touch-sensitivesurfaces, displays, touchscreens), and one or more transducers 114(referred to hereinafter as “the transducers 114”). The electronics 112is configured to receive audio from an audio source (e.g., the localaudio source 105) via the input/output 111, one or more of the computingdevices 106 a-c via the network 104 (FIG. 1B)), amplify the receivedaudio, and output the amplified audio for playback via one or more ofthe transducers 114. In some examples, the playback device 110 aoptionally includes one or more microphones 115 (e.g., a singlemicrophone, a plurality of microphones, a microphone array) (hereinafterreferred to as “the microphones 115”). In certain examples, forinstance, the playback device 110 a having one or more of the optionalmicrophones 115 can operate as an NMD configured to receive voice inputfrom a user and correspondingly perform one or more operations based onthe received voice input.

In the illustrated example of FIG. 1C, the electronics 112 comprise oneor more processors 112 a (referred to hereinafter as “the processors 112a”), memory 112 b, software components 112 c, a network interface 112 d,one or more audio processing components 112 g (referred to hereinafteras “the audio components 112 g”), one or more audio amplifiers 112 h(referred to hereinafter as “the amplifiers 112 h”), and power 112 i(e.g., one or more power supplies, power cables, power receptacles,batteries, induction coils, Power-over Ethernet (POE) interfaces, and/orother suitable sources of electric power). In some examples, theelectronics 112 optionally include one or more other components 112 j(e.g., one or more sensors, video displays, touchscreens, batterycharging bases).

The processors 112 a can comprise clock-driven computing component(s)configured to process data, and the memory 112 b can comprise acomputer-readable medium (e.g., a tangible, non-transitorycomputer-readable medium, data storage loaded with one or more of thesoftware components 112 c) configured to store instructions forperforming various operations and/or functions. The processors 112 a areconfigured to execute the instructions stored on the memory 112 b toperform one or more of the operations. The operations can include, forexample, causing the playback device 110 a to retrieve audio data froman audio source (e.g., one or more of the computing devices 106 a-c(FIG. 1B)), and/or another one of the playback devices 110. In someexamples, the operations further include causing the playback device 110a to send audio data to another one of the playback devices 110 a and/oranother device (e.g., one of the NMDs 120). Certain examples includeoperations causing the playback device 110 a to pair with another of theone or more playback devices 110 to enable a multi-channel audioenvironment (e.g., a stereo pair, a bonded zone).

The processors 112 a can be further configured to perform operationscausing the playback device 110 a to synchronize playback of audiocontent with another of the one or more playback devices 110. As thoseof ordinary skill in the art will appreciate, during synchronousplayback of audio content on a plurality of playback devices, a listenerwill preferably be unable to perceive time-delay differences betweenplayback of the audio content by the playback device 110 a and the otherone or more other playback devices 110. Additional details regardingaudio playback synchronization among playback devices can be found, forexample, in U.S. Pat. No. 8,234,395, which was incorporated by referenceabove.

In some examples, the memory 112 b is further configured to store dataassociated with the playback device 110 a, such as one or more zonesand/or zone groups of which the playback device 110 a is a member, audiosources accessible to the playback device 110 a, and/or a playback queuethat the playback device 110 a (and/or another of the one or moreplayback devices) can be associated with. The stored data can compriseone or more state variables that are periodically updated and used todescribe a state of the playback device 110 a. The memory 112 b can alsoinclude data associated with a state of one or more of the other devices(e.g., the playback devices 110, NMDs 120, control devices 130) of themedia playback system 100. In some examples, for instance, the statedata is shared during predetermined intervals of time (e.g., every 5seconds, every 10 seconds, every 60 seconds) among at least a portion ofthe devices of the media playback system 100, so that one or more of thedevices have the most recent data associated with the media playbacksystem 100.

The network interface 112 d is configured to facilitate a transmissionof data between the playback device 110 a and one or more other deviceson a data network such as, for example, the links 103 and/or the network104 (FIG. 1B). The network interface 112 d is configured to transmit andreceive data corresponding to media content (e.g., audio content, videocontent, text, photographs) and other signals (e.g., non-transitorysignals) comprising digital packet data including an Internet Protocol(IP)-based source address and/or an IP-based destination address. Thenetwork interface 112 d can parse the digital packet data such that theelectronics 112 properly receives and processes the data destined forthe playback device 110 a.

In the illustrated example of FIG. 1C, the network interface 112 dcomprises one or more wireless interfaces 112 e (referred to hereinafteras “the wireless interface 112 e”). The wireless interface 112 e (e.g.,a suitable interface comprising one or more antennae) can be configuredto wirelessly communicate with one or more other devices (e.g., one ormore of the other playback devices 110, NMDs 120, and/or control devices130) that are communicatively coupled to the network 104 (FIG. 1B) inaccordance with a suitable wireless communication protocol (e.g., Wi-Fi,Bluetooth, LTE). In some examples, the network interface 112 doptionally includes a wired interface 112 f (e.g., an interface orreceptacle configured to receive a network cable such as an Ethernet, aUSB-A, USB-C, and/or Thunderbolt cable) configured to communicate over awired connection with other devices in accordance with a suitable wiredcommunication protocol. In certain examples, the network interface 112 dincludes the wired interface 112 f and excludes the wireless interface112 e. In some examples, the electronics 112 excludes the networkinterface 112 d altogether and transmits and receives media contentand/or other data via another communication path (e.g., the input/output111).

The audio components 112 g are configured to process and/or filter datacomprising media content received by the electronics 112 (e.g., via theinput/output 111 and/or the network interface 112 d) to produce outputaudio signals. In some examples, the audio processing components 112 gcomprise, for example, one or more digital-to-analog converters (DAC),audio preprocessing components, audio enhancement components, a digitalsignal processors (DSPs), and/or other suitable audio processingcomponents, modules, circuits, etc. In certain examples, one or more ofthe audio processing components 112 g can comprise one or moresubcomponents of the processors 112 a. In some examples, the electronics112 omits the audio processing components 112 g. In some examples, forinstance, the processors 112 a execute instructions stored on the memory112 b to perform audio processing operations to produce the output audiosignals.

The amplifiers 112 h are configured to receive and amplify the audiooutput signals produced by the audio processing components 112 g and/orthe processors 112 a. The amplifiers 112 h can comprise electronicdevices and/or components configured to amplify audio signals to levelssufficient for driving one or more of the transducers 114. In someexamples, for instance, the amplifiers 112 h include one or moreswitching or class-D power amplifiers. In other examples, however, theamplifiers include one or more other types of power amplifiers (e.g.,linear gain power amplifiers, class-A amplifiers, class-B amplifiers,class-AB amplifiers, class-C amplifiers, class-D amplifiers, class-Eamplifiers, class-F amplifiers, class-G and/or class H amplifiers,and/or another suitable type of power amplifier). In certain examples,the amplifiers 112 h comprise a suitable combination of two or more ofthe foregoing types of power amplifiers. Moreover, in some examples,individual ones of the amplifiers 112 h correspond to individual ones ofthe transducers 114. In other examples, however, the electronics 112includes a single one of the amplifiers 112 h configured to outputamplified audio signals to a plurality of the transducers 114. In someother examples, the electronics 112 omits the amplifiers 112 h.

In the example of FIG. 1C, the playback device 110 a further includestemperature sensor(s) 112 k. The temperature sensor(s) 112 k can includeany device, such as a thermocouple or thermistor, capable of detectingtemperature. In some examples, multiple discrete temperature sensors 112k can be disposed within, on, or about the playback device 110 a indifferent locations and configured to detect local temperatures at oradjacent those locations. For example, temperature sensors 112 k can bedisposed adjacent certain electronic components (e.g., adjacent theprocessor(s) 112 a), transducer components (e.g., adjacent the magnetsof transducers 114), or any suitable location of the playback device. Insome examples, the playback device 110 a includes 1, 2, 3, 4, 5, 6, 7,8, 9, 10 or more discrete temperature sensors 112 k. As described inmore detail below, the temperature sensor(s) 112 k can becommunicatively coupled to the processor(s) 112 a or other suitablecomponents such that, based on data from the temperature sensor(s) 112k, audio playback via the playback device 110 a can be modulated. Forexample, if temperature readings exceed a predetermined threshold, again of the audio playback may be gradually decreased to protect thedevice from thermal damage. Once temperature data obtained via thetemperature sensor(s) 112 k indicates that temperature has fallen belowpre-determined threshold, the gain can be restored.

The transducers 114 (e.g., one or more speakers and/or speaker drivers)receive the amplified audio signals from the amplifier 112 h and renderor output the amplified audio signals as sound (e.g., audible soundwaves having a frequency between about 20 Hertz (Hz) and 20 kilohertz(kHz)). In some examples, the transducers 114 can comprise a singletransducer. In other examples, however, the transducers 114 comprise aplurality of audio transducers. In some examples, the transducers 114comprise more than one type of transducer. For example, the transducers114 can include one or more low frequency transducers (e.g., subwoofers,woofers), mid-range frequency transducers (e.g., mid-range transducers,mid-woofers), and one or more high frequency transducers (e.g., one ormore tweeters). As used herein, “low frequency” can generally refer toaudible frequencies below about 500 Hz, “mid-range frequency” cangenerally refer to audible frequencies between about 500 Hz and about 2kHz, and “high frequency” can generally refer to audible frequenciesabove 2 kHz. In certain examples, however, one or more of thetransducers 114 comprise transducers that do not adhere to the foregoingfrequency ranges. For example, one of the transducers 114 may comprise amid-woofer transducer configured to output sound at frequencies betweenabout 200 Hz and about 5 kHz.

By way of illustration, SONOS, Inc. presently offers (or has offered)for sale certain playback devices including, for example, a “SONOS ONE,”“MOVE,” “PLAY:5,” “BEAM,” “PLAYBAR,” “PLAYBASE,” “PORT,” “BOOST,” “AMP,”and “SUB.” Other suitable playback devices may additionally oralternatively be used to implement the playback devices of exampleexamples disclosed herein. Additionally, one of ordinary skilled in theart will appreciate that a playback device is not limited to theexamples described herein or to SONOS product offerings. In someexamples, for instance, one or more playback devices 110 comprises wiredor wireless headphones (e.g., over-the-ear headphones, on-earheadphones, in-ear earphones). In other examples, one or more of theplayback devices 110 comprise a docking station and/or an interfaceconfigured to interact with a docking station for personal mobile mediaplayback devices. In certain examples, a playback device may be integralto another device or component such as a television, a lighting fixture,or some other device for indoor or outdoor use. In some examples, aplayback device omits a user interface and/or one or more transducers.For example, FIG. 1D is a block diagram of a playback device 110 pcomprising the input/output 111 and electronics 112 without the userinterface 113 or transducers 114.

FIG. 1E is a block diagram of a bonded playback device 110 q comprisingthe playback device 110 a (FIG. 1C) sonically bonded with the playbackdevice 110 i (e.g., a subwoofer) (FIG. 1A). In the illustrated example,the playback devices 110 a and 110 i are separate ones of the playbackdevices 110 housed in separate enclosures. In some examples, however,the bonded playback device 110 q comprises a single enclosure housingboth the playback devices 110 a and 110 i. The bonded playback device110 q can be configured to process and reproduce sound differently thanan unbonded playback device (e.g., the playback device 110 a of FIG. 1C)and/or paired or bonded playback devices (e.g., the playback devices 110l and 110 m of FIG. 1B). In some examples, for instance, the playbackdevice 110 a is full-range playback device configured to render lowfrequency, mid-range frequency, and high frequency audio content, andthe playback device 110 i is a subwoofer configured to render lowfrequency audio content. In some examples, the playback device 110 a,when bonded with the first playback device, is configured to render onlythe mid-range and high frequency components of a particular audiocontent, while the playback device 110 i renders the low frequencycomponent of the particular audio content. In some examples, the bondedplayback device 110 q includes additional playback devices and/oranother bonded playback device. Additional playback device examples aredescribed in further detail below with respect to FIGS. 2A-2C.

c. Suitable Network Microphone Devices (NMDs)

FIG. 1F is a block diagram of the NMD 120 a (FIGS. 1A and 1B). The NMD120 a includes one or more voice processing components 124 (hereinafter“the voice components 124”) and several components described withrespect to the playback device 110 a (FIG. 1C) including the processors112 a, the memory 112 b, and the microphones 115. The NMD 120 aoptionally comprises other components also included in the playbackdevice 110 a (FIG. 1C), such as the user interface 113 and/or thetransducers 114. In some examples, the NMD 120 a is configured as amedia playback device (e.g., one or more of the playback devices 110),and further includes, for example, one or more of the audio components112 g (FIG. 1C), the amplifiers 114, and/or other playback devicecomponents. In certain examples, the NMD 120 a comprises an Internet ofThings (IoT) device such as, for example, a thermostat, alarm panel,fire and/or smoke detector, etc. In some examples, the NMD 120 acomprises the microphones 115, the voice processing components 124, andonly a portion of the components of the electronics 112 described abovewith respect to FIG. 1B. In some examples, for instance, the NMD 120 aincludes the processor 112 a and the memory 112 b (FIG. 1B), whileomitting one or more other components of the electronics 112. In someexamples, the NMD 120 a includes additional components (e.g., one ormore sensors, cameras, thermometers, barometers, hygrometers).

In some examples, an NMD can be integrated into a playback device. FIG.1G is a block diagram of a playback device 110 r comprising an NMD 120d. The playback device 110 r can comprise many or all of the componentsof the playback device 110 a and further include the microphones 115 andvoice processing components 124 (FIG. 1F). The playback device 110 roptionally includes an integrated control device 130 c. The controldevice 130 c can comprise, for example, a user interface (e.g., the userinterface 113 of FIG. 1B) configured to receive user input (e.g., touchinput, voice input) without a separate control device. In otherexamples, however, the playback device 110 r receives commands fromanother control device (e.g., the control device 130 a of FIG. 1B).

Referring again to FIG. 1F, the microphones 115 are configured toacquire, capture, and/or receive sound from an environment (e.g., theenvironment 101 of FIG. 1A) and/or a room in which the NMD 120 a ispositioned. The received sound can include, for example, vocalutterances, audio played back by the NMD 120 a and/or another playbackdevice, background voices, ambient sounds, etc. The microphones 115convert the received sound into electrical signals to produce microphonedata. The voice processing components 124 receive and analyzes themicrophone data to determine whether a voice input is present in themicrophone data. The voice input can comprise, for example, anactivation word followed by an utterance including a user request. Asthose of ordinary skill in the art will appreciate, an activation wordis a word or other audio cue that signifying a user voice input. Forinstance, in querying the AMAZON® VAS, a user might speak the activationword “Alexa.” Other examples include “Ok, Google” for invoking theGOOGLE® VAS and “Hey, Siri” for invoking the APPLE® VAS.

After detecting the activation word, voice processing components 124monitor the microphone data for an accompanying user request in thevoice input. The user request may include, for example, a command tocontrol a third-party device, such as a thermostat (e.g., NEST®thermostat), an illumination device (e.g., a PHILIPS HUE® lightingdevice), or a media playback device (e.g., a Sonos® playback device).For example, a user might speak the activation word “Alexa” followed bythe utterance “set the thermostat to 68 degrees” to set a temperature ina home (e.g., the environment 101 of FIG. 1A). The user might speak thesame activation word followed by the utterance “turn on the living room”to turn on illumination devices in a living room area of the home. Theuser may similarly speak an activation word followed by a request toplay a particular song, an album, or a playlist of music on a playbackdevice in the home.

d. Suitable Control Devices

FIG. 1H is a partially schematic diagram of the control device 130 a(FIGS. 1A and 1B). As used herein, the term “control device” can be usedinterchangeably with “controller” or “control system.” Among otherfeatures, the control device 130 a is configured to receive user inputrelated to the media playback system 100 and, in response, cause one ormore devices in the media playback system 100 to perform an action(s) oroperation(s) corresponding to the user input. In the illustratedexample, the control device 130 a comprises a smartphone (e.g., aniPhone™, an Android phone) on which media playback system controllerapplication software is installed. In some examples, the control device130 a comprises, for example, a tablet (e.g., an iPad™), a computer(e.g., a laptop computer, a desktop computer), and/or another suitabledevice (e.g., a television, an automobile audio head unit, an IoTdevice). In certain examples, the control device 130 a comprises adedicated controller for the media playback system 100. In otherexamples, as described above with respect to FIG. 1G, the control device130 a is integrated into another device in the media playback system 100(e.g., one more of the playback devices 110, NMDs 120, and/or othersuitable devices configured to communicate over a network).

The control device 130 a includes electronics 132, a user interface 133,one or more speakers 134, and one or more microphones 135. Theelectronics 132 comprise one or more processors 132 a (referred tohereinafter as “the processors 132 a”), a memory 132 b, softwarecomponents 132 c, and a network interface 132 d. The processor 132 a canbe configured to perform functions relevant to facilitating user access,control, and configuration of the media playback system 100. The memory132 b can comprise data storage that can be loaded with one or more ofthe software components executable by the processor 132 a to performthose functions. The software components 132 c can comprise applicationsand/or other executable software configured to facilitate control of themedia playback system 100. The memory 112 b can be configured to store,for example, the software components 132 c, media playback systemcontroller application software, and/or other data associated with themedia playback system 100 and the user.

The network interface 132 d is configured to facilitate networkcommunications between the control device 130 a and one or more otherdevices in the media playback system 100, and/or one or more remotedevices. In some examples, the network interface 132 d is configured tooperate according to one or more suitable communication industrystandards (e.g., infrared, radio, wired standards including IEEE 802.3,wireless standards including IEEE 802.11a, 802.11b, 802.11g, 802.11n,802.11ac, 802.15, 4G, LTE). The network interface 132 d can beconfigured, for example, to transmit data to and/or receive data fromthe playback devices 110, the NMDs 120, other ones of the controldevices 130, one of the computing devices 106 of FIG. 1B, devicescomprising one or more other media playback systems, etc. Thetransmitted and/or received data can include, for example, playbackdevice control commands, state variables, playback zone and/or zonegroup configurations. For instance, based on user input received at theuser interface 133, the network interface 132 d can transmit a playbackdevice control command (e.g., volume control, audio playback control,audio content selection) from the control device 130 to one or more ofthe playback devices 110. The network interface 132 d can also transmitand/or receive configuration changes such as, for example,adding/removing one or more playback devices 110 to/from a zone,adding/removing one or more zones to/from a zone group, forming a bondedor consolidated player, separating one or more playback devices from abonded or consolidated player, among others.

The user interface 133 is configured to receive user input and canfacilitate ‘control of the media playback system 100. The user interface133 includes media content art 133 a (e.g., album art, lyrics, videos),a playback status indicator 133 b (e.g., an elapsed and/or remainingtime indicator), media content information region 133 c, a playbackcontrol region 133 d, and a zone indicator 133 e. The media contentinformation region 133 c can include a display of relevant information(e.g., title, artist, album, genre, release year) about media contentcurrently playing and/or media content in a queue or playlist. Theplayback control region 133 d can include selectable (e.g., via touchinput and/or via a cursor or another suitable selector) icons to causeone or more playback devices in a selected playback zone or zone groupto perform playback actions such as, for example, play or pause, fastforward, rewind, skip to next, skip to previous, enter/exit shufflemode, enter/exit repeat mode, enter/exit cross fade mode, etc. Theplayback control region 133 d may also include selectable icons tomodify equalization settings, playback volume, and/or other suitableplayback actions. In the illustrated example, the user interface 133comprises a display presented on a touch screen interface of asmartphone (e.g., an iPhone™, an Android phone). In some examples,however, user interfaces of varying formats, styles, and interactivesequences may alternatively be implemented on one or more networkdevices to provide comparable control access to a media playback system.

The one or more speakers 134 (e.g., one or more transducers) can beconfigured to output sound to the user of the control device 130 a. Insome examples, the one or more speakers comprise individual transducersconfigured to correspondingly output low frequencies, mid-rangefrequencies, and/or high frequencies. In some examples, for instance,the control device 130 a is configured as a playback device (e.g., oneof the playback devices 110). Similarly, in some examples the controldevice 130 a is configured as an NMD (e.g., one of the NMDs 120),receiving voice commands and other sounds via the one or moremicrophones 135.

The one or more microphones 135 can comprise, for example, one or morecondenser microphones, electret condenser microphones, dynamicmicrophones, and/or other suitable types of microphones or transducers.In some examples, two or more of the microphones 135 are arranged tocapture location information of an audio source (e.g., voice, audiblesound) and/or configured to facilitate filtering of background noise.Moreover, in certain examples, the control device 130 a is configured tooperate as playback device and an NMD. In other examples, however, thecontrol device 130 a omits the one or more speakers 134 and/or the oneor more microphones 135. For instance, the control device 130 a maycomprise a device (e.g., a thermostat, an IoT device, a network device)comprising a portion of the electronics 132 and the user interface 133(e.g., a touch screen) without any speakers or microphones.

III. Example Systems and Methods for Thermal Control of Playback Devices

FIG. 2A is a front isometric view of a playback device 210 configured inaccordance with examples of the disclosed technology. FIG. 2B is a frontisometric view of the playback device 210 without a grille 216 e. FIG.2C is an exploded view of the playback device 210. Referring to FIGS.2A-2C together, the playback device 210 comprises a housing 216 thatincludes an upper portion 216 a, a right or first side portion 216 b, alower portion 216 c, a left or second side portion 216 d, the grille 216e, and a rear portion 216 f. A plurality of fasteners 216 g (e.g., oneor more screws, rivets, clips) attaches a frame 216 h to the housing216. A cavity 216 j (FIG. 2C) in the housing 216 is configured toreceive the frame 216 h and electronics 212. The frame 216 h isconfigured to carry a plurality of transducers 214 (identifiedindividually in FIG. 2B as transducers 214 a-f). The electronics 212(e.g., the electronics 112 of FIG. 1C) is configured to receive audiocontent from an audio source and send electrical signals correspondingto the audio content to the transducers 214 for playback.

The transducers 214 are configured to receive the electrical signalsfrom the electronics 112, and further configured to convert the receivedelectrical signals into audible sound during playback. For instance, thetransducers 214 a-c (e.g., tweeters) can be configured to output highfrequency sound (e.g., sound waves having a frequency greater than about2 kHz). The transducers 214 d-f (e.g., mid-woofers, woofers, midrangespeakers) can be configured output sound at frequencies lower than thetransducers 214 a-c (e.g., sound waves having a frequency lower thanabout 2 kHz). In some examples, the playback device 210 includes anumber of transducers different than those illustrated in FIGS. 2A-2C.For example, as described in further detail below with respect to FIGS.3A-3C, the playback device 210 can include fewer than six transducers(e.g., one, two, three). In other examples, however, the playback device210 includes more than six transducers (e.g., nine, ten). Moreover, insome examples, all or a portion of the transducers 214 are configured tooperate as a phased array to desirably adjust (e.g., narrow or widen) aradiation pattern of the transducers 214, thereby altering a user'sperception of the sound emitted from the playback device 210.

In the illustrated example of FIGS. 2A-2C, a filter 216 i is axiallyaligned with the transducer 214 b. The filter 216 i can be configured todesirably attenuate a predetermined range of frequencies that thetransducer 214 b outputs to improve sound quality and a perceived soundstage output collectively by the transducers 214. In some examples,however, the playback device 210 omits the filter 216 i. In otherexamples, the playback device 210 includes one or more additionalfilters aligned with the transducers 214 b and/or at least another ofthe transducers 214.

As seen in FIG. 2C, a plurality of temperature sensors 212 k can bedisposed within the playback device 210. For example, the temperaturesensors 212 k can be coupled to the electronics 212. However, in someexamples, one or more of the temperature sensors 212 k can be disposedin other positions, such as on or adjacent to the transducers 214, or onor adjacent to the housing 216. The temperature sensors 212 k can be anysuitable devices configured to detect temperature, such as thermocouplesor thermistors. In operation, temperature data obtained via thetemperature sensors 212 k can be used to modulate operation of theplayback device 210 to reduce the risk of thermal damage. For example, again of audio playback can be temporarily reduced based on temperaturedata obtained via one or more of the temperature sensors 212 k, asdescribed in more detail elsewhere herein.

FIG. 3 is a schematic block diagram of a system 300 for thermal controlof a playback device. The system 300 includes a plurality of temperaturesensors 302 a-n (collectively “sensors 302”) that provide input (e.g.,temperature data) to a thermal controller 304. The thermal controller304, in turn, provides an output (e.g., a modulation parameter such asan amount of gain reduction) to a modulator 312. The modulator 312 canmodulate operation of the playback device (e.g., by reducing gain ofaudio playback), which proceeds with audio playback in block 314.

The thermal controller 304 can include, for example, instructions storedin memory (e.g. memory 112 b of FIG. 1C) executed by one or moreprocessors (e.g., processor(s) 112 a of FIG. 1C). The modulator 312 canbe included within the audio processing components 112 g (FIG. 1C)and/or the audio amplifiers 112 h (FIG. 1C). In some examples, thethermal controller 304 and/or the modulator 312 can be discretecomponents that are separate from the processor 112 a, audio processingcomponents 112 g, and/or audio amplifiers 112 h.

As noted above, in some examples, a playback device can include aplurality of temperature sensors 302 disposed on, within, or about theplayback device. In various implementations, the number of temperaturesensors 302 can vary, for example, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10 or moretemperature sensors. The temperature sensors 302 may includethermocouples, thermistors, or any other suitable sensor configured todetect temperature. The temperature sensors 302 can provide data to thethermal controller 304. The output data can include temperaturereadings, such as absolute temperature readings, relative temperaturereadings (e.g., temperature increase or decrease relative to theprevious sample), etc. In some examples, the temperature sensors 302 caneach output temperature data at a sampling rate. For example, thetemperature sensors 302 can output temperature data to the thermalcontroller 304 at a sampling rate of one temperature reading every 1, 2,3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or every 20seconds. The sampling rate may be the same for some or all of thetemperature sensors 302, or the sampling rate may vary among some or allof the temperature sensors 302.

In some examples, the temperature sensors 302 be configured such thatthe temperature data provided by the sensors 302 is quantized. Forinstance, the temperature sensors 302 can be configured to outputtemperature data in increments of 1 degree C. (or other suitablequantity). As described in more detail elsewhere herein, thisquantization can be used to assess whether data from one or moretemperature sensors 302 indicates the playback device to be in a rising,steady, or falling thermal state, and may also be used to determine orcharacterize a rate of increase or decrease in temperature. Thequantization may be the same for some or all of the temperature sensors302, or the quantization may vary among some or all of the temperaturesensors 302.

In some cases, temperature data obtained via the temperature sensors 302can be “debounced” to reduce or eliminate noise in the temperaturereadings. For example, relatively small changes in temperature data(e.g., a change at the lowest quantization, such as 1 degree C.) may bediscarded until they persist for a predetermined time or a predeterminednumber of samples. In some examples, changes of temperature at thelowest detectable increment (e.g., 1 degree C.) may be discarded untilthey persist for at least 30 seconds, at least 1 minute, at least 90seconds, or at least 2 minutes.

As shown in FIG. 3 , the temperature data from each sensor 302 can besupplied to the thermal controller 304 to generate respectivetemperature parameters 306 a, 306 b, and 306 n (collectively“temperature parameters 306”). The temperature parameters 306 can becalculated or determined based on input from the temperature sensors 302and used to characterize one or both of (1) a real-time (orsubstantially real-time) indication of the temperature at thattemperature senor and (2) a rate or gradient of the temperature changeat that temperature sensor.

In some examples, the temperature parameters 306 can include a rate orgradient of change of the temperature over time, based on data obtainedvia the respective temperature sensors 302. For example, the temperatureparameters 306 can include a rate of change (e.g., degrees C. persecond). Additionally or alternatively, the temperature parameters 306can include a temperature inverse gradient (i.e., a time elapsed sincethe last detected temperature change of at least a pre-determined amount(e.g., at least about 0.5, 1, 1.5, 2.0, 2.5 degrees C.)). Characterizinga time elapsed since the last temperature change of a predeterminedamount (e.g., the time elapsed since the last temperature increase of atleast 1 degree C.) can indicate a rate of temperature increase, withsmaller time elapsed indicating a higher rate of temperature increase.As described below, operation of the playback device can be modulated toa greater or lesser degree depending on this characterization. If thetemperature is deemed to be increasing rapidly, greater modulation(e.g., higher gain reduction) may be warranted. Conversely, if thetemperature is deemed to be increasingly slowly or remaining steady,operation of the playback device may be modulated more incrementally(e.g., lower levels of gain reduction), even if the temperature exceedsa pre-determined threshold at which modulation may be initiated.

In some embodiments, using an inverse temperature gradient (e.g., a timeelapsed over which the temperature rises by a pre-determined amount) canprovide certain advantages over other parameters, such as an absoluterate of temperature change. For example, an inverse temperature gradientis relatively easy to measure using standard sensor components.Additionally, for most heating processes typical to a playback device,using a temperature inverse gradient allows one to easily predict afinal temperature (in the absence of intervention) and how long it willtake the playback device to reach that temperature. This in turn allowsone to quickly estimate the power reduction (or other modulation) neededto prevent the playback device from exceeding the maximum allowablethreshold temperature.

The temperature parameters 306 may then be used to determine orcalculate respective modulation parameters 308 a, 308 b, and 308 n(collectively “modulation parameters 308”). These modulation parameters308 can include a potential modulation of operation of the playbackdevice based on the particular temperature parameter 306. As notedelsewhere herein, modulation of operation of the playback device caninclude one or more of: reduction (or increase) of gain of audioplayback across the full spectrum, a reduction (or increase) of gain ofaudio playback in a manner that varies across frequency ranges, areduction (or increase) in wireless communication (e.g., throttlingWi-Fi or Bluetooth transmission or reception), or any other modificationof operation of the playback device that may affect the temperature ofthe playback device.

In some examples, the thermal controller 304 is configured such thatmodulation of audio playback is performed only within particulartemperature ranges. For example, below a first or lower temperaturethreshold (e.g., no temperature sensor 302 indicates a temperature at orabove the lower temperature threshold), there may be no modulation ofthe playback device. As such, the modulation parameters 308 may each be0 or otherwise indicate no modification of operation of the playbackdevice. In this state, the thermal controller 304 may effectively be apassive component, having no effect on operation of the playback device.This reflects a condition in which the playback device is deemed to beoperating within safe temperature levels, and no temperature sensorindicates a temperature level that poses risk to components of theplayback device. In various examples, this first or lower temperaturethreshold can be about 20, 25, 30, 35, 40, 45, 50, 55, 60, 65, or about70 degrees C. In some examples, the lower temperature threshold can bethe same for some or all of the temperature sensors 302. In someexamples, the lower temperature threshold can vary among some or all ofthe temperature sensors 302.

Additionally or alternatively, the thermal controller 304 is configuredsuch, above a second or upper temperature threshold, audio playback isceased completely, and/or the playback device is shut down completely.As such, the modulation parameter 308 associated with any temperaturesensor whose data exceeds the upper threshold can indicate a partial ortotal shutdown of the playback device. Based on this modulationparameter 308, the modulator 312 can cease audio playback and/orcompletely shut down operation of the playback device. This uppertemperature threshold can reflect a maximum safe operating temperature,such that exceeding this temperature threshold may inflict permanentdamage to components of the playback device. In various examples, thissecond or upper temperature threshold can be about 35, 40, 45, 50, 55,60, 65, 70, 75, 80, 85, 90, 95, 100, 105, 110, 115, or about 120 degreesC. In some examples, the upper temperature threshold can be the same forsome or all of the temperature sensors 302. In some examples, the uppertemperature threshold can vary among some or all of the temperaturesensors 302.

The lower temperature threshold and upper temperature threshold cantogether define an operating range in which the thermal controllermodulates operation of the playback device (e.g., by reducing gain). Insome embodiments, the difference between the lower temperature thresholdand the upper temperature threshold can be about 2, 3, 4, 5, 6, 7, 8, 9,10, 11, 12, 13, 14, 15, 16, 17, 18, 19, or 20 degrees C. or more.

As noted previously, the particular modulation parameters 308characterizing an amount or degree of modulation (e.g., an amount ofgain reduction) may vary depending on the corresponding temperatureparameters 306. In some examples, the temperature parameters 306 canindicate both on an absolute temperature (e.g., whether the temperatureis above or below the lower threshold and whether the temperature isabove, at, near, or below the upper threshold) as well as the change orrate of change of the temperature. As described in more detail belowwith respect to FIG. 4 , the particular modulation may depend on whetherthe temperature is deemed to be rising, falling, or steady.Additionally, the degree of modulation (e.g., the amount of gainreduction) can vary depending on the amount or rate of temperaturechange. For example, if the temperature is rising more rapidly (e.g.,less time elapsed since the last detected temperature increase of atleast 1 degree C.), the gain may be reduced by a greater amount than ifthe temperature is rising more slowly or is remaining steady.

With continued reference to FIG. 3 , each of the modulation parameters308 may reflect a different potential modification of operation of theplayback device. For example, the first modulation parameter 308 a mayoutput a gain reduction of 0.1 dB, the second modulation parameter mayoutput a gain reduction of 2 dB, and the nth modulation parameter 308 nmay output a gain reduction of 0 dB (i.e., no gain reduction). Thesevarious modulation parameters 308 can be output to a combiner 310, whichmay then output a single modulation parameter or instruction to themodulator 312. In some examples, the combiner 310 can select thegreatest modulation from among the modulation parameters 308 and providethat parameter to the modulator 312. For example, in the case ofmodulation parameters 308 of 0.1 dB, 2 dB, and 0 dB, the combiner 310may output a gain reduction of 2 dB to the modulator 312, which may thenmodulate the gain accordingly. In some examples, the combiner 310 maycombine the modulation parameters 308 in other ways, for example byweighting the various parameters 308, taking an average of theparameters 308, or other suitable amalgamation of the incomingmodulation parameters 308 to output a particular instruction to themodulator 312.

In operation, the temperature sensors 302 obtain temperature data thatcan be used to determine whether the lower temperature threshold hasbeen exceeded. To reduce the risk of any damage from increasedtemperatures, once the lower threshold has been exceeded, the thermalcontroller 304 can initiate modulation of playback device operation(e.g., by reducing gain by an amount dependent on the particulartemperature parameters 306). If, following the modulation, thetemperature falls below the lower temperature threshold, then themodulation (e.g., gain reduction) can cease, and the playback device canresume normal operation. If, instead, the temperature stays above thelower temperature threshold, then device operation can continue to bemodulated via the thermal controller, with the degree of modulation(e.g., amount of gain reduction) depending on the new temperature dataobtained via the sensors. For example, as the temperature continues toincrease beyond the lower temperature threshold, the amount of gainreduction can be increasingly large. If the temperature continues toincrease and further exceeds the upper temperature threshold (e.g., amaximum safe operating temperature of the playback device), audioplayback or other device operation can be suspended and/or the devicemay be shut down completely.

FIG. 4 is a flow diagram of a process 400 for thermal control of aplayback device. In some embodiments, the process 400 includes one ormore instructions stored in memory (e.g., the memory 112 b of FIG. 1 )and executed by one or more processors (e.g., the processor 112 a ofFIG. 1 ) of a playback device (e.g., the playback device 110 of FIG. 1 ,the playback device 205 of FIG. 2 ). Although the blocks are shown in aparticular order, in some embodiments the steps may be performed indifferent orders. Additionally or alternatively, certain blocks may beomitted, combined, or sub-divided into separate blocks.

In block 402, the temperature data is obtained via one or moretemperature sensors. As noted previously, one or more temperaturesensors can be disposed on, within, or about the playback device andconfigured to detect temperature. The temperature sensors cancontinuously provide temperature data at a sampling rate, for exampleone temperature reading every 5 seconds, 10 seconds, 15 seconds, etc.

In block 404, temperature parameter(s) are determined based on the dataobtained via the temperature sensor(s). As described previously, thetemperature parameter can characterize both an absolute temperaturebased on the temperature data and a change in the temperature data overtime. For example, the temperature parameter can indicate whether thetemperature at any particular sensor is above, at, or below a lowertemperature threshold (e.g., a temperature above which gain reduction orother modulation of playback device operation may be initiated), as wellas whether the temperature is below, near, at, or above an uppertemperature threshold (e.g., a maximum safe operating temperature, abovewhich a playback device may be shut down to avoid permanent damage).Additionally, the temperature parameter can characterize a change intemperature over time, such as classifying the temperature at any givensensor as rising, falling, or remaining steady.

The process 400 continues to decision block 406 with determining whetherthe temperature is rising, steady, or falling. If the temperature issteady (e.g., the temperature has not changed over N samples or haschanged by less than a threshold amount over N samples), the process 400proceeds to decision block 408 to determine whether the temperature isnear the upper threshold. If the temperature is near (e.g., within 0, 1,2, 3, 4, or 5 degrees C.) the upper threshold, then the gain is reducedin block 410. This reflects a state in which, although the temperatureis steady, it remains close to the upper threshold (e.g., the maximumsafe operating temperature). Accordingly, it can be beneficial toincrementally reduce the gain of audio playback in an attempt to lowerthe temperature of the device further away from the upper threshold. Thegain reduction in block 410 can be any suitable amount. In someexamples, the gain reduction in block 410 is relatively small, forexample, about 0.05, 0.1, 0.15, 0.2, or about 0.25 dB. Following thisgain reduction in block 410, the process returns to block 402 withobtaining new temperature data via the temperature sensor(s).

Returning to decision block 408, if the steady temperature is not nearthe upper threshold, the process 400 continues with determining, inblock 412, whether the temperature is above the lower threshold (e.g.,the temperature above which gain modulation may be initiated). If thetemperature is above the threshold, then the process 400 continues toblock 410 with decreasing gain of audio playback. In this manner, steadystate temperature that is above the lower threshold can continue to belowered by decreasing the gain of audio playback.

If, in block 412, the temperature is not above the lower threshold, theprocess 400 continues to block 414 to determine whether current gainreduction is applied. For example, if a prior iteration of the process400 has resulted in gain reduction, then the process 400 would proceedto block 416 with increasing the gain. In this scenario, the gain hasbeen previously reduced (e.g., a gain value less than unity) because ofexcessive temperature. However, as the temperature is now a steady state(block 406) and is below both the upper threshold (block 408) and thelower threshold (block 412), the gain can be increased. In someexamples, the gain can be increased by an incremental amount (e.g., 0.1dB) or may be increased to unity (e.g., restored to a pre-modulationlevel). Following the gain increase in block 418, the process 400returns to block 402 with obtaining new temperature data via thetemperature sensor(s).

If, in block 414, if there is no current gain reduction applied, theprocess 400 continues to block 418 with no modulation of audio playback.This scenario reflects a playback device with a steady-state temperatureand no gain reduction applied. As such, the thermal controller need notalter operation of the playback device and audio playback can proceed asnormal.

Returning to block 406, if the temperature is found to be falling, theprocess 400 continues to block 414 with determining whether current gainreduction is applied. If so, the process 400 continues to block 416 toincrease gain. If no current gain reduction is applied (block 414), theprocess continues in block 418 with no modulation of audio playback.This flow reflects a scenario in which temperature is falling andaccordingly risk of thermal damage to the playback device is low. Assuch, audio playback either proceeds without any modulation (block 418),or any prior-effected gain reduction is at least partially removed orcounteracted via a gain increase in block 416.

If, in block 406, the temperature is rising, the process 400 continuesto block 420 with determining whether the temperature is above the lowerthreshold (e.g., the temperature above which gain reduction may beinitiated). If the temperature is not above this threshold, then theprocess 400 continues to block 418 with no modulation of audio playback.This reflects the scenario in which the temperature, although rising, isbelow the lower threshold and as such considered safe for normaloperation of the playback device.

If the temperature is above the lower threshold in block 420, theprocess 400 continues to block 422 with determining whether thetemperature is below the upper threshold (e.g., the maximum safeoperating temperature of the playback device). If the temperature is ator above this threshold, the process 400 terminates in block 424 withshutting down operation of the playback device. This reflects a failsafescenario in which, to avoid permanent damage to the playback device, thedevice is partially or completely shut down in response to the uppertemperature threshold being met or exceeded.

If the temperature is below the upper threshold in block 422, then theprocess 400 continues to block 426 with decreasing gain of audioplayback based on the temperature parameter (block 404). As notedpreviously, the temperature parameter can include a rate or otherindicia of the change of temperature. In some examples, the temperatureparameter includes a time elapsed since the last detected increase intemperature of at least a predetermined amount. As this time decreases(reflecting a faster increase in temperature), the amount of gainreduction can be increased in block 426.

For example, a function, lookup table, or other approach can be used todefine particular gain reductions in terms of the time elapsed since thelast temperature change of a pre-determined amount. For instance, alookup table as shown in Table 1 below can be used to determine the gainreduction (in dB) applied to audio playback.

TABLE 1 Time since last rise of 1° C. (seconds) Gain Adjustment (dB)500+ −0.1 200  −0.5 80 −1 60 −2  3 −4 <3 −8

This table illustrates one example of increasing gain adjustment with anincrease in the detected rate of rising temperature. In variousexamples, the particular amount of gain reduction in response to variousmagnitudes of temperature rise can vary to achieve the desired thermalfeedback loop. Following gain reduction applied in block 426, theprocess 400 returns to block 402 with obtaining new temperature data viathe temperature sensor(s).

The iterative process 400 can continue to repeat (absent playback deviceshutdown as in block 424), thereby maintaining the playback devicewithin safe operating conditions by incrementally reducing the gain ofaudio playback in response to rising temperature levels (block 426) orpersisting elevated temperature levels (block 410), while restoring thegain to pre-reduction levels once temperatures are either steady orfalling (block 416).

FIGS. 5 and 6 illustrate exemplary data from modeling certain examplesof the thermal controllers disclosed herein. FIG. 5 is a graph showinggain reduction over time during thermal control processes and FIG. 6 isa graph showing temperature over time during the same processes. Togenerate these graphs, a SONOS PLAY:5 playback device was modeled withan idle temperature of 30 degrees C. that was subjected to two thermalevents: first an increase to a final temperature of 98 degrees C.(beginning at t=0 hours) and second an increase to a final temperatureof 108 degrees C. (beginning at approximately t=8.25 hours). For eachevent, five different thermal controllers were modeled as Models 1-5,with respective upper temperature thresholds of 40, 50, 80, 90, and 105degrees C., and respective lower temperature thresholds of 37, 47, 77,87, and 102 degrees C.

As shown in FIG. 5 , starting at t=0, the first thermal increase eventbegins and the temperature rises across all 5 models. As the temperatureexceeds the lower temperature threshold (and approaches the uppertemperature threshold) for each model, gain reduction is initiated (asreflected in FIG. 6 ) to maintain the device temperature within anoperating range below the corresponding upper temperature threshold.Because Model 1 has the lowest upper temperature threshold (40 degreesC.), the gain reduction applied via Model 1 is greatest, with decreasinggain reductions applied for each subsequent model as the respectivetemperature thresholds increase. The maximum temperature of the firstthermal event (98 degrees C.) is less than the lower temperaturethreshold of Model 5; as such, the thermal controller of Model 5 appliesno gain reduction during the first thermal event. As the temperatureevent ceases (at approximately t=2.75 hours), the temperatureexponentially decays, and the corresponding gain reductions applied viaeach model likewise are gradually reduced until returning to 0.

Similarly, in response to the second thermal event (beginning atapproximately t=8.25 hours), each of the thermal controllers shown asModels 1-5 initiates gain reduction as the respective lower thresholdsare exceeded. In this instance, the maximum temperature (108 degrees C.)exceeds the lower threshold of all models, including Model 5, and assuch all models apply gain reduction to audio playback to maintain thedevice temperature below their respective upper threshold levels. Asseen in FIGS. 5 and 6 , in various examples, a thermal controller can beselected and configured to maintain a playback device safely withindesired operating temperatures by gradually and incrementally applyinggain reduction to audio playback until the temperature decreasessufficiently to restore normal device operation.

IV. Conclusion

The above discussions relating to playback devices, controller devices,playback zone configurations, and media content sources provide onlysome examples of operating environments within which functions andmethods described below may be implemented. Other operating environmentsand/or configurations of media playback systems, playback devices, andnetwork devices not explicitly described herein may also be applicableand suitable for implementation of the functions and methods.

The description above discloses, among other things, various examplesystems, methods, apparatus, and articles of manufacture including,among other components, firmware and/or software executed on hardware.It is understood that such examples are merely illustrative and shouldnot be considered as limiting. For example, it is contemplated that anyor all of the firmware, hardware, and/or software examples or componentscan be embodied exclusively in hardware, exclusively in software,exclusively in firmware, or in any combination of hardware, software,and/or firmware. Accordingly, the examples provided are not the onlyways) to implement such systems, methods, apparatus, and/or articles ofmanufacture.

Additionally, references herein to “example” means that a particularfeature, structure, or characteristic described in connection with theexample can be included in at least one example of an invention. Theappearances of this phrase in various places in the specification arenot necessarily all referring to the same example or example, nor areseparate or alternative examples or examples mutually exclusive of otherexamples or examples. As such, the examples described herein, explicitlyand implicitly understood by one skilled in the art, can be combinedwith other examples.

The specification is presented largely in terms of illustrativeenvironments, systems, procedures, steps, logic blocks, processing, andother symbolic representations that directly or indirectly resemble theoperations of data processing devices coupled to networks. These processdescriptions and representations are typically used by those skilled inthe art to most effectively convey the substance of their work to othersskilled in the art. Numerous specific details are set forth to provide athorough understanding of the present disclosure. However, it isunderstood to those skilled in the art that certain examples of thepresent disclosure can be practiced without certain, specific details.In other instances, well known methods, procedures, components, andcircuitry have not been described in detail to avoid unnecessarilyobscuring examples of the examples. Accordingly, the scope of thepresent disclosure is defined by the appended claims rather than theforegoing description of examples.

When any of the appended claims are read to cover a purely softwareand/or firmware implementation, at least one of the elements in at leastone example is hereby expressly defined to include a tangible,non-transitory medium such as a memory, DVD, CD, Blu-ray, and so on,storing the software and/or firmware.

The disclosed technology is illustrated, for example, according tovarious Clauses described below. Various examples of examples of thedisclosed technology are described as numbered Clauses (1, 2, 3, etc.)for convenience. These are provided as examples and do not limit thedisclosed technology. It is noted that any of the dependent Clauses maybe combined in any combination, and placed into a respective independentClauses. The other Clauses can be presented in a similar manner.

Clause 1. A method of thermal control of a playback device, the methodcomprising: obtaining, via one or more temperature sensors carried bythe playback device, temperature data; based on the temperature data,detecting a first temperature parameter indicating a first increase intemperature; in response to detecting the first temperature parameter,decreasing a gain of audio playback by a first amount; after decreasingthe gain of audio playback by the first amount, detecting a secondtemperature parameter indicating a second increase in temperature; inresponse to detecting the second temperature parameter, furtherdecreasing a gain of audio playback by a second amount different thanthe first amount.

Clause 2. The method of any one of the Clauses herein, wherein detectingthe first temperature parameter comprises determining a rate oftemperature increase.

Clause 3. The method of any one of the Clauses herein, wherein detectingthe first temperature parameter comprises determining a time since alast detected temperature increase of at least a predetermined amount.

Clause 4. The method of any one of the Clauses herein, wherein an amountof gain reduction applied via decreasing the gain of audio playback bythe first amount is based at least in part on the determined time.

Clause 5. The method of any one of the Clauses herein, furthercomprising determining that the temperature data has fallen below apredetermined temperature threshold and, based at least in part on thedetermination, increasing a gain of audio playback.

Clause 6. The method of any one of the Clauses herein, wherein theplayback device is a first playback device bonded with a second playbackdevice for synchronous playback, the method further comprisingdecreasing a gain of audio playback via the second playback deviceconcurrently with decreasing the gain of audio playback via the firstplayback device by the first amount.

Clause 7. The method of any one of the Clauses herein, furthercomprising: obtaining temperature data from each of a plurality oftemperature sensors carried by the playback device; for each temperaturesensor, detecting a temperature parameter; for each temperature sensor,determining an amount of gain reduction to be applied to audio playbackbased on the detected temperature parameter; decreasing a gain of audioplayback by the first amount, wherein the first amount comprises thelargest gain reduction from among the gain reductions determined foreach of the temperature sensors.

Clause 8. The method of any one of the Clauses herein, wherein obtainingtemperature data comprises obtaining temperature data from one or morevirtual sensors.

Clause 9. A playback device comprising: one or more temperature sensors;at least one audio transducer; one or more processors; and acomputer-readable memory storing instructions that, when executed by theone or more processors, cause the playback device to perform operationscomprising: the method of any one of the Clauses herein.

Clause 10. Tangible, non-transitory computer-readable medium storinginstructions that, when executed by the one or more processors of aplayback device, cause the playback device to perform operationscomprising: the method of any one of the Clauses herein.

The invention claimed is:
 1. A playback device comprising: a pluralityof temperature sensors; at least one audio transducer; one or moreprocessors; and a computer-readable memory storing instructions that,when executed by the one or more processors, cause the playback deviceto perform operations comprising: obtaining temperature data from eachof the plurality temperature sensors; based on the temperature data,obtaining a temperature parameter for each of the plurality oftemperature sensors, at least one of the temperature parametersindicating an increase in temperature; for each temperature sensor,determining an amount of gain reduction to be applied to audio playbackbased on the temperature parameter; and decreasing a gain of audioplayback by a first amount, wherein the first amount comprises thelargest gain reduction from among the gain reductions determined foreach of the temperature sensors.
 2. The playback device of claim 1,wherein the playback device is a first playback device bonded with asecond playback device for synchronous playback, the operations furthercomprising decreasing a gain of audio playback via the second playbackdevice concurrently with decreasing the gain of audio playback via thefirst playback device by the first amount.
 3. The playback device ofclaim 1, wherein the operations further comprise, after decreasing thegain, determining that the temperature data has fallen below apredetermined temperature threshold and, based at least in part on thedetermination, increasing a gain of audio playback.
 4. The playbackdevice of claim 1, wherein the operations further comprise, afterdecreasing the gain, determining that the temperature data is fallingand, based at least in part on the determination, increasing the gain ofaudio playback.
 5. The playback device of claim 1, wherein theoperations further comprise, after decreasing the gain, determining thatthe temperature data has risen above a predetermined threshold and,based at least in part on the determination, shutting down the playbackdevice.
 6. The playback device of claim 1, wherein the operationsfurther comprise, after decreasing the gain, determining that thetemperature is steady near an upper threshold and, based at least inpart on the determination, further decreasing the gain of audioplayback.
 7. The playback device of claim 1, wherein detecting thetemperature parameter comprises determining a time since a last detectedtemperature increase of at least a predetermined amount.
 8. A method ofthermal control of a playback device, the method comprising: obtainingtemperature data from each of a plurality of temperature sensors carriedby the playback device; based on the temperature data, obtaining atemperature parameter for each of the plurality of temperature sensors,at least one of the temperature parameters indicating an increase intemperature; for each temperature sensor, determining an amount of gainreduction to be applied to audio playback based on the temperatureparameter; and decreasing a gain of audio playback by a first amount,wherein the first amount comprises the largest gain reduction from amongthe gain reductions determined for each of the temperature sensors. 9.The method of claim 8, wherein the playback device is a first playbackdevice bonded with a second playback device for synchronous playback,the method further comprising decreasing a gain of audio playback viathe second playback device concurrently with decreasing the gain ofaudio playback via the first playback device by the first amount. 10.The method of claim 8, further comprising, after decreasing the gain,determining that the temperature data has fallen below a predeterminedtemperature threshold and, based at least in part on the determination,increasing a gain of audio playback.
 11. The method of claim 8, furthercomprising, after decreasing the gain, determining that the temperaturedata is falling and, based at least in part on the determination,increasing the gain of audio playback.
 12. The method of claim 8,further comprising, after decreasing the gain, determining that thetemperature data has risen above a predetermined threshold and, based atleast in part on the determination, shutting down the playback device.13. The method of claim 8, further comprising, after decreasing thegain, determining that the temperature is steady near an upper thresholdand, based at least in part on the determination, further decreasing thegain of audio playback.
 14. The method of claim 8, wherein detecting thetemperature parameter comprises determining a time since a last detectedtemperature increase of at least a predetermined amount.
 15. One or moretangible, non-transitory computer-readable media storing instructionsthat, when executed by one or more processors of a playback device,cause the playback device to perform operations comprising: obtainingtemperature data from each of a plurality of temperature sensors carriedby the playback device; based on the temperature data, obtaining atemperature parameter for each of the plurality of temperature sensors,at least one of the temperature parameters indicating an increase intemperature; for each temperature sensor, determining an amount of gainreduction to be applied to audio playback based on the temperatureparameter; and decreasing a gain of audio playback by a first amount,wherein the first amount comprises the largest gain reduction from amongthe gain reductions determined for each of the temperature sensors. 16.The one or more computer-readable media of claim 15, wherein theplayback device is a first playback device bonded with a second playbackdevice for synchronous playback, the operations further comprisingdecreasing a gain of audio playback via the second playback deviceconcurrently with decreasing the gain of audio playback via the firstplayback device by the first amount.
 17. The one or morecomputer-readable media of claim 15, wherein the operations furthercomprise, after decreasing the gain, determining that the temperaturedata has fallen below a predetermined temperature threshold and, basedat least in part on the determination, increasing a gain of audioplayback.
 18. The one or more computer-readable media of claim 15,wherein the operations further comprise, after decreasing the gain,determining that the temperature data is falling and, based at least inpart on the determination, increasing the gain of audio playback. 19.The one or more computer-readable media of claim 15, wherein theoperations further comprise, after decreasing the gain, determining thatthe temperature data has risen above a predetermined threshold and,based at least in part on the determination, shutting down the playbackdevice.
 20. The one or more computer-readable media of claim 15, whereinthe operations further comprise, after decreasing the gain, determiningthat the temperature is steady near an upper threshold and, based atleast in part on the determination, further decreasing the gain of audioplayback.